The present invention relates to an improved method and associated apparatus for friction welding of components.
In particular the present invention relates to rotary friction welding and non-rotary motion friction welding, providing means for controlling ductilities of the components during the welding process so as to bias the welding process in favour of a first component or to match the ductilities of different components thereby facilitating the welding process.
Rotary friction welding and non-rotary motion friction welding are used to create solid state welds. By moving a first component relative to a second component, the interface between them is heated via friction. When the ductility of the materials are sufficiently reduced by this heating, the components are squeezed together, expelling material from the interface to form an upset and creating conditions suitable for a pressure weld to form.
Used correctly friction welding provides high integrity welds with low porosity and contamination. Furthermore, friction welding is a solid state process that does not melt but only softens the components being joined, permitting the joining of material combinations that cannot be otherwise welded and of joining cast materials that suffer degradation if recast.
However, as used hitherto the process has limitations. Up to now it has not been possible to join all material combinations, in particular where components to be joined are of widely disparate ductilities. For example attempts to join titanium aluminide component to a titanium component generally fail as the titanium aluminide component cannot be heated sufficiently by friction before the titanium component begins to melt.
A further limitation can be caused by the upset resulting from the friction welding process. Although the upset performs a useful role, removing contamination prior to weld formation, upset consumes material from both components being joined according to their ductility. Hence friction welding two similar components results in similar material loss from each and conversely when welding materials of different ductility, the upset consumes more material from the softer component, the change in geometry associated with both the material consumed and the upset itself mean that the process is not suitable to repair of geometry-critical components.
The present invention seeks to provide control of component ductilities and thereby provide an improved friction welding process to overcome the above limitations. Furthermore it enables the friction welding process to be biased to consume more material from a less critical component regardless of the relative ductilities of the components being joined.
According to one aspect of the present invention there is provided friction welding apparatus for friction welding a first component and a second component together, the first component having a first weld face, the second component having a second weld face, the apparatus comprising means for bringing together the first weld face of the first component and the second weld face of the second component under a load to form a weld interface, means for simultaneously moving at least one of the components relative to the other to generate frictional heat at the weld interface, and cooling means to control temperatures in the first component adjacent the first weld face in order to control ductility of the first component adjacent the weld interface.
According to a further aspect of the present invention such apparatus is provided with heating means to increase temperatures in the second component adjacent the second weld face thereby controlling ductility of the second component adjacent the interface.
According to another aspect of the present invention there is provided a method of friction welding a first component and a second component together, the first component having a first weld face, the second component having a second weld face, comprising the steps of bringing together the first weld face of the first component and second weld face of the second component under a load to form a weld interface, simultaneously moving at least one of the components relative to the other to generate frictional heat at the weld interface, and cooling the first component adjacent the first weld face thereby controlling the ductility of the first component adjacent the weld interface.
According to a further aspect of the present invention, there is provided such a method of friction welding wherein the second component is heated adjacent the second weld face thereby controlling the ductility of the second component adjacent the weld interface.
The invention and how it may be carried out in practise will now be described in more detail with reference to the accompanying drawings in which: